Audi R8 e-tron: Electric Supercar Boogaloo
From the outside it has the same lusciously seductive profile as the R8 supercar. The only indication that something might me different about the R8 e-tron is the cooling-air outlet in the hood, and the absence of tail pipes. Although they look almost identical, the two cars share only nine common parts. Once the R8 e-tron gets moving, its almost-dead silence is a giveaway to its electric propulsion system.
Of course if you were to strip the bright red paint from the bodywork you’d also notice that a large proportion of the outer skin is made from lightweight carbon fibre. Lift the body panels and you’ll find a very light aluminum chassis—even the suspension coil springs are made of fibreglass-reinforced polymer. The body structure weighs just 199 kg, 23 kilos lighter than the body of the R8.
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All of these weight-saving measures are necessary to compensate for the 530-cell lithium-ion battery pack, which runs down the centre of the car and spreads out in a T behind the driver. The R8 e-tron weighs in at 1,780 kg, a significant 155 kg heavier than the R8 V8 Coupé with a manual transmission. One benefit of the electric R8 is that most of its weight is concentrated very low in the chassis which gives it a significantly lower centre of gravity.
Two 140 kW electric motors are located at the rear axle, one driving each rear wheel through a planetary gearset. Combined the motors produce 380 horsepower and an incredibly potent 605 lb.-ft. of torque, which is available as soon as the motors begin to spin. Torque is further increased through a gear reduction in the planetary gearset, giving the R8 e-tron the capability to accelerate from 1 to 100 km/h in just 4.2 seconds. That’s just two tenths shy of the 0-100 km/h time of the 525-horsepower R8 V10.
Electric power has its limitations, however, and top speed is restricted to 200 km/h. The R8 e-tron is capable of attaining 260 km/h without restriction, but running at any speed above 200 km/h would drain the batteries in a matter of minutes. Driving normally the R8 e-tron has a range of 215 km, which is nowhere near the potential 425-km range of the Tesla Model S, but it is more than the i-MiEV and Nissan Leaf. Charging the drained batteries takes 12 hours at 230 volts AC.
As with all electric cars, regenerative braking serves to slow the R8 e-tron down from speed, but for serious stopping power there are large, hydraulically operated carbon-fibre ceramic front discs. Things get interesting in the rear, where electromechanical-screw disc brakes are used. These brakes are electrically controlled for high precision and they control power to the rear wheels for torque vectoring capability in turns.
Audi allowed me an opportunity to drive the R8 e-tron on a course set out at Berlin’s Tempelhof airport.
Well, the first thing you’ll notice about the R8 e-tron is the gut-flattening, eyeball-squashing acceleration, which seems even more impressive because of the seamless power delivery. In fact, it almost sounded like it had a small engine when accelerating hard from a stop because of the howl produced by the tires as they struggled for grip, and by the mechanical growl of the planetary gearset as it transferred all of that torque to the ground.
Corner-exit drive is almost beyond reproach due to the car’s low centre of gravity, which favours rear weight transfer. The R8 e-tron lapped the short twisty course like a toy slot car, with remarkable steering precision and phenomenal grip in corners. As a lapping toy, this car is truly hard to beat. The only thing missing is the symphony of an angry V8 or V10 put an accent on the experience.
The unfortunate thing about the Audi R8 e-tron is that no matter how much money you can afford to spend to add it to your collection of exotic sports cars, you’ll never be able to buy one. Although Audi began the project with the intention of making it a production model, it has proven too expensive to produce and the project was dropped. That’s not to say that some of the electric technology won’t transfer to other cars, and Audi will be bringing the A3 e-tron hybrid to Canada in 2014, so not all is lost.
When asked how much it cost to produce the R8 e-tron, the answer was unequivocal: “It is not economically viable to produce.” That’s a shame really, because aside from its limited top speed, it is truly an exhilarating automobile to drive.